JPS5915767B2 - end mill - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in end mills.

With conventional end mills, the cutting edge extends approximately on the radius of the end mill, resulting in almost two-dimensional cutting, which causes a strong impact force to act on the end mill cutting edge, easily damaging the cutting edge, making high-speed heavy cutting impossible. .

In other words, with conventional end mills, when the end mill rotates to cut, all parts of the blade, from the center to the outer periphery, come into contact with the workpiece almost simultaneously, which increases the impact force during cutting and easily damages the cutting edge. , heavy cutting was also impossible.

In addition, in recent years, rigid materials such as shapes have become increasingly hard and difficult to cut, so it has become necessary to use cemented carbide for end mill processing. There is a problem that the cutting edge is damaged.

For this reason, when a cemented carbide is used for an end mill, the cutting speed near the center is slow even if the end mill is rotated at high speed, so chipping of the cutting edge near the center is unavoidable.

Furthermore, with conventional cutting edge shapes, the chips generated during cutting remain attached to the rake face before the next cut is made.
When these adhered chips are removed, the cutting edge is likely to chip.

For these reasons, it has conventionally been considered impossible to use cemented carbide in ball end mills, and their use has been limited to those similar to manual engraving machines that perform micro-cutting at high speed.

An object of the present invention is to solve the above problems and provide an end mill that can withstand high-speed heavy cutting.

Next, embodiments of the present invention will be described based on the drawings.

The end mill body 10 consists of a shank 11 and a spherical tip 12.

A balance wheel 20 is fixed to the tip portion 12.

The balance wheel 20 has a roughly rectangular plate shape, when viewed from the front (Fig. 1).
It has a vertically long rectangular shape when viewed from the bottom (FIG. 2) (when viewed from below in the direction of the rotation axis of the end mill).

The positional relationship with the main body tip 12 is such that, when viewed from the bottom, the first long side surface 21 is placed on the radius of the end mill, and one corner 2
6 is placed on the end mill center 0, and the first short side surface 23 is
This is a state in which the end mill is located on the forward side relative to the long side surface 21 in the rotation direction R of the end mill.

Then, the second long side surface 22 becomes a rake surface, and the second rectangular side surface 2
4 becomes the flank of the tip side, and the tip curved surface 25 becomes the flank of the tip of the tip.

Moreover, the cutting edges formed at the tips of the second long side surface 22 and the first rectangular side surface 23 are continuous with a smooth curve to form a tip cutting edge 27, which is followed by the second long side surface 22. The boundary edge with the second short side surface 24 is defined as a side cutting edge 28.

That is, when viewed from the bottom, the cutting edge 27 at the tip has a smooth curve or a curved line that is convex toward the forward direction in the rotational direction of the end mill with respect to a straight line connecting the starting end of the cutting blade at the center of the end mill and the terminal end of the cutting blade on the outer periphery of the end mill. Draw a smooth joining line or broken line with a straight line.

Therefore, the tip cutting edge 27 performs three-dimensional cutting, and the cutting force acting on the cutting edge is significantly reduced, making it possible to sufficiently withstand high-speed heavy cutting.

Furthermore, in the illustrated case, the blade angle C of the side cutting blade 28 and the blade angle of the tip cutting blade 27 are approximately 90 degrees, resulting in a very strong blade edge.

This is because, as mentioned above, since the cutting edge 27 draws a convex line in the direction of rotation when viewed from the bottom, a relief angle can exist even if the blade angle is 90 degrees, and it is also possible to select a dog blade angle. be.

Moreover, since the first short side surface 23 is located on the forward side in the end mill rotation direction R, the thickness from the cutting edge 27 to the right end of the main body 10 increases in FIG. This increases the strength of the cutting edge.

As shown in Fig. 9, the cutting edge line is approximately 0.7R from the cutting edge starting point 0 ( If A1 is the angle of the tangent to the radius of the cutter (R is the radius of the cutter), then it changes smoothly with the following relationship: Ao = 75°, A1 = -15°, and AO - A1 = 90°.

However, angle A. . For A1, the value measured in the direction of rotation from the straight line is positive.

A theoretical explanation of the cutting process by the end mill having this configuration is as follows.

First of all, in a normal end mill, as shown in Fig. 6 a and b,
When the workpiece W is sent in the direction of the arrow and the end mill E rotates clockwise to perform cutting, the straight cutting edge 27 appears at point A when viewed from the bottom.
The full length of the blade a begins contact with the workpiece W almost at the same time, and cutting begins through an elastic and plastic sliding process, reaches the maximum depth of cut at point B, and ends at point 0.

Since the cuts are made at the same time near point A, the end mill bends greatly and chips W.

As shown in Fig. 6, when viewed from the side, the chips are gathered in the normal direction of the arc and compressed, the rake face receives great pressure, and the chips are heated and welded to create cutting resistance, which prevents damage to the cutting edge. stop.

In order to make it easier to understand the cutting process of the end mill according to the embodiment of the present application, assuming that AQ=90° and disassembling it, the seventh
As shown in Figures a and e, contact cutting begins from the center of the tip of the cutting edge at the zero point.

Since the speed of the cutting edge in this part is close to zero, the cutting edge gradually cuts from a very small width, producing cutting chips Wo, and no slippage occurs.

When the central part of the cutting edge reaches the OB line as shown in g, the outer peripheral part of the cutting edge comes into contact with the workpiece.

During this time, the end mill E rotates 90 degrees, and cutting is performed gradually and continuously, which explains why there is little impact.

Next, when the outer peripheral part reaches the maximum cutting point B as shown in c and h, the central cutting edge finishes cutting and is located at the 0 point, and the chips are
One end begins to separate from the workpiece material, and this phenomenon continues continuously until the outer periphery reaches the zero point as shown in d and i.

Between points 0 and C', as shown in e and j, the rake face of the end mill is a chip W that is slightly connected to the workpiece near the 0 point.

Using that part as a fulcrum, it is reversed by the normal component force f shown in the figure and discharged so as not to interfere with the next cutting.

Assuming the cutting resistance of the end mill during rotation, the result will be as shown in FIG. 8.

That is, the cutting section T during one rotation of the blade is T=Ao+1
The relationship is 80° = 90° + 180° = 270°,
The cutting force increases gradually.

This is because the end mill of the present application has a cutting edge curve with a large curvature at the center, and cutting is performed gradually from the center (cutting edge tip).

In other words, whereas conventional end mills start cutting almost simultaneously from the center to the outer periphery, and therefore apply a large impact force at the beginning of cutting, the end mill of the present invention starts cutting gradually from the center to the outer periphery. Because of this, impact force is generated, and cutting begins smoothly without causing any elastic or plastic slippage.

In addition, in the tip cutting edge 27, the cutting point gradually moves from the center to the outer periphery, so that three-dimensional cutting is performed, so the cutting force acting on the cutting edge is significantly reduced, making it suitable for high-speed heavy cutting. Be patient enough.

Furthermore, in the illustrated case, the blade angle C of the side cutting edge 28 and the blade angle C of the tip cutting edge are 90°, resulting in a very strong cutting edge.

This is because, as described above, since the cutting edge 27 draws a convex line in the direction of rotation when viewed from the bottom, a relief angle can exist even if the cutting edge angle is 90 degrees.

In this way, with the present invention, it is possible to easily perform 16 cuts at the center of the tip of a ball end mill, which has been a particular problem in the past, and the area near the center has been cut into a curved line instead of a straight line. By doing so, it is possible to make the cutting easier, and also to gradually perform the cutting to prevent the cutting resistance from increasing suddenly.

Therefore, if the value of Ao-A1 at the cutting edge line is too small, the effect will be reduced.

This can be explained by the measurement results of the stress acting mutually between the work material and the cutting edge shown in FIGS. 10 and 11.

Figure 10 shows the resultant force of the component force in the feed direction of the workpiece and the component force in the surface direction of the workpiece perpendicular to it, where 1 is the conventional product;
2 is a product of the present invention with an angle of (Ao-A1) of 150°, and 3 is a product of the present invention (A).

-A1) is shown with an angle of 35°.

Curve 1 rises rapidly as the rotational force of the end mill progresses and reaches its peak, whereas curve 2 shows a gentle rise. In contrast, with the product of the present invention, the load increases gradually, no impact load is applied at the beginning of cutting, and the maximum load is small because the cutting starts gradually.

And the angle of (Ao A1) is 35° (curve 3)
However, the increase in load is more gradual than with conventional products, indicating that it is time to start cutting down gradually.

FIG. 11 shows the component force in the axial direction of the end mill, with the direction in which the tip presses the workpiece downward as positive, and the direction in which the tip pulls the workpiece upward as negative.

Curve 4 shows the force component of the conventional product, and curve 5 shows the force component of the product of the present invention. From this, it can be seen that the conventional product starts to experience a considerable top-slip phenomenon at the beginning of cutting, whereas the product of the present invention does not have a top-slip phenomenon at the beginning of cutting. do not have.

In other words, the stress measurement results also show that with the conventional product, cutting begins after the top-slip phenomenon, and a sudden load is applied at the start of cutting, but with the product of the present invention, cutting begins immediately, and cutting gradually increases until the maximum cutting point is reached. It can be seen that no impact load is applied to the cutting edge.

Even when the (AOAI) angle is 35 degrees (curve 6), the upward slip phenomenon is significantly reduced compared to the conventional product, and cutting is started smoothly.

In the above embodiment, only the case where the balance wheel 20 is installed vertically (the side cutting blade 28 is vertical in FIG. 1) has been described, but it is also possible to install it at a slight inclination. Of course.

As described above, the present invention has an extremely simple structure, which was impossible in the past.

The cutting performance of the present invention is completely amazing, as high-speed heavy cutting is possible and chip evacuation is extremely smooth.

[Brief explanation of the drawing]

Fig. 1 is a front view of an embodiment of the present invention, Fig. 2 is a bottom view, Fig. 3 is a left side view, and Figs. 4 and 5 are Fig. 2 A-A and B-, respectively.
B sectional view, FIG. 6 a is a projection view of the bottom surface of the conventional end mill onto the upper surface of the workpiece, FIG. 6 is a longitudinal sectional view along the workpiece feeding direction, and FIGS. An explanatory diagram similar to Figure a, Figures 7 f to j are explanatory diagrams similar to the end mill of the present invention,
Figure 8 is a comparison graph of cutting resistance, Figure 9 is a bottom view of the product of the present invention, Figure 10 is a horizontal resistance force distribution diagram during cutting between the product of the present invention and the conventional product, and Figure 11 is in the vertical direction. FIG. 10...Body, 11...Shank, 1
2... Tip, 20... Balance, 27
...Tip cutting edge, 28...Side cutting blade.

Claims (1)

[Claims] 1 In a single-flute ball end mill, the starting end of the cutting edge is near the rotation center of the end mill, and when viewed from the bottom of the end mill, the cutting edge forms a convex curve with respect to the rotation direction, and the cutting edge curve on the outer periphery of the end mill is located at the center. An end mill characterized in that the cutting edge curve at the end has a larger curvature.